Multilayer printed wiring board and process for producing the same

ABSTRACT

At least one base material having a wiring circuit that has been formed into a predetermined outer shape is bonded to a motherboard. The motherboard wiring board and the base material having a wiring circuit are electrically connected to each other at least one portion through an inner via hole. The outer shape of the base material having a wiring circuit is smaller than the outer shape of the motherboard, with the base material having a wiring circuit having an island shape on the motherboard.

TECHNICAL FIELD

The present invention relates to a multi-layer wiring board and a methodfor manufacturing the same.

BACKGROUND ART

Recent electronic apparatuses have been made smaller and light weight inaddition to developments in the applicability to high-frequency signalsand digitized devices, and along with these developments, there havebeen demands for small-size devices, a high-density packaging propertyand the like in printed circuit boards being installed in the electronicapparatuses.

There is a rigid flex printed circuit board satisfying these demandswhich includes a rigid portion and a flex portion (for example, JapanesePatent Application Laid Open Publication No. 2002-158445).

With reference to FIGS. 1A to 2B, a manufacturing process of aconventional rigid flex printed circuit board will be described bellow.FIGS. 1A to 1D are flow charts that show manufacturing processes of therigid flex printed circuit board. FIG. 2A is a perspective view thatshows the substrate and the like shown in FIGS. 1A and 1B and FIG. 2B isa perspective view of a rigid flex wiring board shown in FIG. 1D.

As shown in FIG. 1A, wiring circuits 104 are formed by a subtractivemethod on both of the surfaces of a flex substrate 101 made of apolyimide film, both of the surfaces of an inner-layer rigid substrate102 made from a prepreg and the like, and one surface of an outer layerrigid substrate 103.

Substantially, as shown in FIG. 1A and FIG. 2A, flex-portion exposingholes 109 are formed through a bonding sheet 105, the inner-layer rigidsubstrate 102 and the outer-layer rigid substrate 103, by using apress-punching process and the like. Next, a flex-substrate-use coverlayer 106, the inner-layer rigid substrate 102, the bonding sheet 105and the outer-layer rigid substrate 103 are superposed and placed on thesurface and rear surface of the flex substrate 101, and subjected to alaminating process to prepare a laminated member 100 shown in FIG. 1B.In this case, as shown in FIG. 2A, a peripheral portion of a portion(for example, indicated by 103 a) that forms a circuit board uponcompletion of the processes is punched out so that the portion (forexample, 103 a) to form the circuit board is joined to a frame member(for example, 103 b) by using a micro-joint (for example, 103 c).

Next, as shown in FIG. 1C, the laminated member 100 is subjected to adrilling process, a plating process and etching so that a through hole107, an outer-layer wiring circuit 108 and the like are formed therein.

Lastly, the micro-joints (for example, 103 c), which have joined a rigidportion B and a flex portion A to the frame member (for example, 103 b),are simultaneously punched out by using a die so that a rigid flexprinted circuit board 110, shown in FIGS. 1D and 2B, is obtained. Inthis case, the frame member (for example, 103 b) for the substrates 101,102 and 103 and portions that have been punched out so as to form thesubstrates 101 are disposed.

Moreover, those circuit boards having an arrangement in which a built-uplayer is formed on the surface layer of the rigid flex printed circuitboard, and interlayer-connected thereto through IVHS (Interstitial ViaHoles) and SVHS (Surface Via Holes) have also been proposed.

DISCLOSURE OF INVENTION

However, according to the conventional rigid flex printed circuit boardand the manufacturing method thereof, after the lamination of the rigidportion, the outer shapes of the rigid portion and the flex portion needto be simultaneously cut out (a cutting process). Therefore, it isnecessary to use substrates having sufficient margin portions requiredfor positioning processes for the respective substrates. Moreover, inmost of cases, after the cutting process, these margin portions aredisposed as the frame members. In other words, in the conventional rigidflex printed circuit board, since the rigid portion needs to belaminated at a predetermined position of the flex substrate, assemblingprocesses of the rigid portions on the inner layer and outer layer rigidsubstrates, which are carried out so as to place the rigid portions atpredetermined positions on the flex substrate when formed as laminatedlayers, are limited by factors such as an outer shape and positions ofthe flex substrate. In other words, even when an attempt is made so asto carry out a laminating process only on one portion of the flexsubstrate, it is necessary to prepare an assembling-use member that isas large as the flex substrate.

For this reason, excessive multi-layered areas exist on the rigidportion, causing wasteful material costs. Further, there is a limitationin positions in which multi-layered areas are placed, resulting inlittle design freedom for wiring.

The present invention has been devised to solve the above-mentionedproblems, and the first objective thereof is to provide a multi-layerwiring board which provides higher design freedom for wiring, and makesit possible to cut material costs, and also to reduce the substratecapacity, and a manufacturing method for such a wiring board.

In order to achieve the above-mentioned objects, according to a firstaspect of a multi-layer wiring board, wherein at least one base materialwith wiring circuit being preliminarily formed into a predeterminedouter shape is bonded to a motherboard, and the base material on themotherboards are electrically connected to each other through at leastan inner via hole.

Moreover, conventionally, when a substrate that includes a plurality ofsubstrates with single-sided wiring circuits is bent, a separation tendsto occur between the substrates due to inter-layer stress of the layersof the motherboard printed substrate and the substrate with single-sidedwiring circuits or between the layers of the laminated substrates withsingle-sided wiring circuits.

Therefore, a second object of the present invention is to provide amulti-layer wiring board which has higher anti-bending strength (peelstrength) as compared with the conventional substrate, and amanufacturing method for such a wiring board

In order to achieve this objective, according to a second aspect of amulti-layer wiring board, wherein two or more substrates, each of whichhas been preliminarily formed into a predetermined outer shape withsingle-sided wiring circuit formed thereon, are laminated and bonded toa motherboard, and at least one inter-layer portion thereof iselectrically connected through an inner via hole, and in thisarrangement, the two or more laminated substrates, each withsingle-sided wiring circuit formed thereon, are positioned in a mannerso as to place the outer shape of a second substrate bonded to the firstsubstrate inside the outer shape of the first substrate being bonded tothe motherboard side

Moreover, in the case when a circuit substrate that allows double-sidedassembling processes is formed by using the conventional manufacturingmethod, a double-sided circuit substrate is required as a coresubstrate. In the case, however, as described above, upon forming aconductive pattern, most of the conductive layer on one side needs to beremoved, resulting in wasteful use of materials and resources. Anotherproblem is that complex manufacturing processes are required to formthrough holes and the like.

Therefore, a third object of the present invention is to provide acircuit substrate that allows double-sided packaging processes so thatelectronic parts can be assembled on double sides by using asingle-sided circuit substrate as a core substrate (main circuitsubstrate), that is, as a motherboard

In order to achieve this object, according to a third aspect of amulti-layer wiring board, wherein at least one portion of an insulatingbase material of a main single-sided circuit substrate having aconductive pattern on one surface of the insulating substrate ispartially removed so that the rear face of the conductive pattern isexposed at the removed portion, and from the other side of theinsulating base material of the main single-sided circuit substrate, anelectronic part is laminated with the main single-sided circuitsubstrate with the rear-face exposed portion of the conductive patternof the main single-sided circuit substrate is electrically connect withthe electrical part, and/or a single-sided circuit board for multi-layerwiring board having an interlayer conductive portion and a conductivepattern formed on one face of an insulating base material is laminatedwith the main single-sided circuit substrate with the rear-faceexposed-portion of the conductive pattern is electrically connect withthe single-sided circuit board for multi-layer wiring board.

Furthermore, the conventional printed wiring board that allowsdouble-sided packaging processes uses a double-sided copper coatlaminated plate (double-sided CCL) as a starting member for a relayboard. In this technique, however, since plated through holes are used,time-consuming complex metal plating processes are required, and thethickness of a copper foil of the double-sided CCL tends to increase,causing the problem that it is difficult to form a fine pattern throughchemical etching. Moreover, it is difficult to form a via hole to theupper layer or the like right above a through hole, and circuitdesigning is, ipso, restricted.

In order to solve this problem, a fourth object of the present inventionis to provide a multi-layer wiring board that allows double-sidedpackaging processes so that electronic parts can be assembled on doublesides by using a base material with single-sided circuit substrateformed thereon as a starting member for a relay board, and amanufacturing method for such a multi-layer wiring board

In order to achieve this object, according to a fourth aspect of amulti-layer wiring board, a multi-layer wiring board having wiring boardfor partial multi-layers formed on a specific area in a relay boardformed by a base material with single-sided wiring circuit, and therelay board has a conductive layer on one face of an insulatingsubstrate, an interlayer connecting portion comprising a via hole formedon the insulating substrate and filled with a conductive substance, andan interlayer connecting portion comprising a via hole formed on theinsulating resin layer, and wherein the multi-layer-use substrates arelaminated on respective specific areas on the face on the side oppositeto the conductive layer face of the insulating base material and thesurface of the insulating resin layer with, in conductive-associationwith the relay board.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A to 1D are flow charts that show manufacturing processes of aconventional rigid flex printed wiring board.

FIG. 2A is a perspective view of FIGS. 1A and 1B.

FIG. 2B is a perspective view of the rigid flex printed wiring boardshown in FIG. 1D.

FIG. 3 is a cross-sectional view that shows a first embodiment of amulti-layer wiring board in accordance with the present invention.

FIG. 4 is a plan view that shows the first embodiment of the multi-layerwiring board in accordance with the present invention.

FIG. 5 is a cross-sectional view that shows a modified example of thefirst embodiment of the multi-layer wiring board in accordance with thepresent invention.

FIG. 6 is a cross-sectional view that shows a modified example of thefirst embodiment of the multi-layer wiring board in accordance with thepresent invention.

FIG. 7 is a cross-sectional view that shows a modified example of thefirst embodiment of the multi-layer wiring board in accordance with thepresent invention.

FIG. 8 is a cross-sectional view that shows a modified example of thefirst embodiment of the multi-layer wiring board in accordance with thepresent invention.

FIG. 9 is a cross-sectional view that shows a modified example of thefirst embodiment of the multi-layer wiring board in accordance with thepresent invention.

FIG. 10 is a cross-sectional view that shows a modified example of thefirst embodiment of the multi-layer wiring board in accordance with thepresent invention.

FIGS. 11A to 11F are flow charts that show a manufacturing method for aresin base material with single-sided wiring circuit, which is used fora multi-layer wiring board in accordance with the first embodiment ofthe present invention.

FIGS. 12A to 12C are flow charts that show a manufacturing method forthe multi-layer wiring board in accordance with the first embodiment ofthe present invention.

FIGS. 13A and 13B are flow charts that show a manufacturing method for amulti-layer wiring board in accordance with a modified example of thefirst embodiment.

FIGS. 14A to 14E are flow charts that show a manufacturing method for amulti-layer wiring board in accordance with another modified example ofthe first embodiment.

FIG. 15 is a cross-sectional view that shows a multi-layer wiring boardin accordance with a second embodiment of the present invention.

FIG. 16 is a plan view that shows the multi-layer wiring board inaccordance with the second embodiment of the present invention.

FIG. 17 is an explanatory drawing that schematically shows a bent stateof the multi-layer wiring board in accordance with the second embodimentof the present invention.

FIGS. 18A to 18F are flow charts that show a manufacturing method for aresin base material with single-sided wiring circuit, which is used forthe multi-layer wiring board in accordance with the second embodiment ofthe present invention.

FIGS. 19A to 19C are flow charts that show a manufacturing method forthe multi-layer wiring board in accordance with the second embodiment ofthe present invention.

FIG. 20 is a cross-sectional view that shows a multi-layer wiring boardin accordance with a third embodiment of the present invention.

FIG. 21 is a plan view that shows the multi-layer wiring board inaccordance with the third embodiment of the present invention.

FIGS. 22A to 22E are flow charts that show manufacturing processes of amotherboard that is used for the multi-layer wiring board in accordancewith the third embodiment of the present invention.

FIG. 23 is a plan view that schematically shows the motherboard that isused for the multi-layer wiring board in accordance with the thirdembodiment of the present invention.

FIGS. 24A to 24F are flow charts that show manufacturing processes for asingle-sided circuit board for multi-layer wiring board to be used inthe multi-layer wiring board in accordance with the third embodiment.

FIGS. 25A to 25C are flow charts that show laminating processes of thesingle-sided circuit board for multi-layer wiring board in accordancewith the third embodiment of the present invention.

FIG. 26 is a cross-sectional view that shows a modified example of themulti-layer wiring board d in accordance with the third embodiment ofthe present invention.

FIG. 27 is a cross-sectional view that shows a multi-layer wiring boardin accordance with a fourth embodiment of the present invention.

FIG. 28 is a plan view that schematically shows the multi-layer wiringboard in accordance with the fourth embodiment of the present invention.

FIGS. 29A to 29E are flow charts that show manufacturing processes for arelay board to be used in the multi-layer wiring board in accordancewith the fourth embodiment of the present invention.

FIG. 30 is a cross-sectional view that shows a wiring board for partialmulti-layer to be used in the multi-layer wiring board in accordancewith the fourth embodiment of present invention.

FIGS. 31A to 31C are flow charts that show laminating processes of themulti-layer wiring board in accordance with the fourth embodiment of thepresent invention.

FIG. 32 is a cross-sectional view that shows one embodiment of acircuit-forming transfer tape to be used in the multi-layer wiring boardin accordance with the fourth embodiment of the present invention.

FIGS. 33A to 33C are flow charts that show laminating processes of themulti-layer wiring board in which the circuit-forming transfer tape foruse in the multi-layer wiring board is used, in accordance with thefourth embodiment of the present invention.

FIG. 34 is a cross-sectional view that shows a partial multi-layersubstrate for use in an outer layer, which is used for the fourthembodiment of the present invention.

FIGS. 35A to 35C are flow charts that show laminating processes of themulti-layer writing substrate in which the partial multi-layer-formingsubstrate for use in an outer layer is used, in accordance with thefourth embodiment of the present invention.

FIG. 36 is a cross-sectional view that shows a modified example of themulti-layer wiring board in accordance with the fourth embodiment of thepresent invention.

FIGS. 37A to 37E are flow charts that show manufacturing processes of arelay board to be used in the modified example of the multi-layer wiringboard in accordance with the fourth embodiment of the present invention.

FIG. 38 is a cross-sectional view that shows a partialmulti-layer-forming substrate to be used in the modified example of themulti-layer wiring board in accordance with the fourth embodiment of thepresent invention.

FIGS. 39A to 39C are flow charts that show laminating processes of amodified example of the multi-layer wiring board in accordance with thefourth embodiment of the present invention.

BEST MODE FOR CARRYING OUT INVENTION

With reference to Figures, embodiments of the present invention will bedescribed below.

First Embodiment

FIGS. 3 and 4 show a basic mode of a multi-layer wiring board inaccordance with a first embodiment of the present invention. In themulti-layer wiring board of the present embodiment, at a plurality ofportions on the surface and rear surface of a motherboard (basematerial) 10, partial wiring boards (multi-layer portions) 20, whichhave outer shapes that have been preliminarily formed into predeterminedshapes, and will be described later, are bonded so as to form an islandshape. Here, the island shape is defined as a state in which theperipheral sides of the partial wiring boards 20 are not coincident withthe peripheral sides of the motherboard 10 so that the partial wiringboards 20 are placed inside the area which is defined by the peripheralsides of the motherboard 10. Additionally, the predetermined shapes aredetermined on the request of designing the motherboard.

The partial wiring boards 20 are formed as follows: a plurality of resinbase materials 21 with single-sided wiring circuits accordingly, whichhave outer shapes that have been formed into predetermined shapes thatare smaller than the outer shape of the motherboard 10, are positionedon the surface and rear surface of the motherboard 10, and thencolaminated. Here, the partial wiring boards 20 may include resin basematerials with double-sided wiring circuits

The motherboard 10 is provided with an insulating base material 11 andconductor layers (wiring circuits) 12 formed on the surface and rearsurface of the insulating base material 11. The insulating base material11 of the motherboard 10 is made from a flexible resin such aspolyimide. Additionally, with respect to the flexible resin, othermaterials, such as liquid crystal polymer (LCP), polyether imide (PEI),polyether ether ketone (PEEK), polyethylene naphthalate (PEN),polyethylene terephthalate (PET) and polyether sulfone (PES), may beused. The resin base material 21 with single-sided wiring circuit isprovided with an insulating base material 22, and a conductor layer(wiring circuit) 23 formed on one surface of the insulating basematerial 22. Besides rigid prepreg, the insulating base material 22 ofthe resin base material 21 with single-sided wiring circuit may be madefrom a flexible resin such as polyimide.

The conductor layers 23 of the resin base materials 21 with single-sidedwiring circuits formed into a multi-layer structure, as well as theconductor layers 23 of the resin base materials 21 with single-sidedwiring circuits and the conductor layer 12 of the motherboard 10, areelectrically connected to each other by a conductor 25 being filled withconductive paste and the like coating inner via holes (via hole) 24 arerespectively formed in the resin base materials 21 with single-sidedwiring circuits.

The multi-layer wiring board is manufactured by layering the resin basematerials 21 with single-sided wiring circuits that have outer shapesthat have been formed into predetermined shapes to one portion of thesurface and/or the rear surface of the motherboard 10. Morespecifically, a build-up method in which the resin base materials 21with single-sided wiring circuits are bonded to one after another sheetby sheet may be used, however, a colamination method in which aplurality of resin base materials 21 with single-sided wiring circuits,each of which has a wiring circuit and a via hole formed thereon, andhas an outer shape that has been formed into a predetermined shape, aresuperposed on the surface or one portion of the rear surface of themotherboard 10, and bonded to one after another by heating and pressingthese through a batch process is more preferably used since it is asimpler method and can be achieved at low costs.

The mutual layering process between the resin base materials 21 withsingle-sided wiring circuits, the layering process between the resinbase materials 21 with single-sided wiring circuits and the motherboard10 can be carried out by a layering layer (not shown) being formed on anoverside opposite to the conductor layer 23 of the insulating basematerial 22 of each of the resin base materials 21 with single-sidedwiring circuits. In the case when the insulating base material 22 ofeach of the resin base materials 21 with single-sided wiring circuits ismade from a material having an adhesive property, such as thermoplasticpolyimide, thermoplastic polyimide to which a thermosetting property isimparted or liquid crystal polymer, the above-mentioned layering layercan be omitted.

With these arrangements, electronic-component-packaging-usemulti-layer-forming portions (partial wiring boards 20) can be freelyplaced on desired positions on the surface of the motherboard 10, and itbecomes possible to reduce excessive multi-layer-forming portions, andconsequently to greatly cut the material costs.

In particular, in the case when the electronic-part packaging portionsare made from an expensive material such as polyimide in response torequirements such as better dielectric properties, light weight andthinness, the above-mentioned arrangements exert greater effects.

Moreover, in the above-mentioned substrate structures, the insulatinglayer (insulating base material 22) of the partial wiring board 20performing as an electronic part packaging portion and the insulatinglayer (insulating base material 11) of a flex portion (motherboard 10)are preferably made from the same material so that the thermal andmechanical properties of the two layers are made coincident with eachother, and therefore, it becomes possible to provide high reliability inthermal and mechanical properties.

In general, the motherboard 10 is coated with a cover layer or a solderresist to protect the conductor layer. With respect to the coveringlayer of the motherboard 10, an opening portion is preliminarily formedat a portion on which multiple layers are formed by the resin basematerials 21 with single-sided wiring circuits, and the resin basematerials 21 with single-sided wiring circuits may be bonded onto thisopening portion. In this case, as shown in FIG. 5, in the openingportion 13A, a gap g is formed between the multi-layer portion(installed portion of partial wiring boards 20) and the covering layer13. And in this gap g portion, the conductor layer 12 is exposed(externally exposed state).

Therefore, in this case, the exposed portion is coated with noble metal15 such as gold as shown in FIG. 6 to prevent oxidation, or as shown inFIG. 7, this portion is preferably coated with a covering layer 16 madefrom solder resist or the like.

Moreover, as shown in FIG. 8, after the layering processes of themulti-layer portions, the covering layer 16 is formed, the coveringlayer 16 coats one portion of the motherboard 10 and the multi-layerportions, thus, for example, in the case when the motherboard wiringboard is flexible, even at the time of bending, it is possible toprevent separation occurring on the interface between the multi-layerportions and the bending portion.

Furthermore, in an attempt to simplify processes, as shown in FIG. 9,this is achieved by integrally molding the cover layer of themotherboard 10 and the insulating layer of each resin base material 21with single-sided wiring circuit that is made in contact with themotherboard 10 and bonded thereto from above. More specifically, theinsulating layer of the resin base material 21 with single-sided wiringcircuit and the cover layer of the motherboard 20 are made of the sameinsulating layer 17, and these are bonded to the motherboard 10.

Moreover, the inner via hole 24 having a structure as shown in FIG. 10is used as a conductive paste inner hole and an air-releasing pore 27having a diameter smaller than that of the resin substrate portion isformed through the conductor layer 23 portion of the resin base material21 with single-sided wiring circuit so that it is possible to preventresidual void at the time of injecting conductive paste. The conductivepaste is also injected into the pore 27 to prevent the pore 27 fromforming a void. Additionally, in FIG. 10, reference numeral 26 indicatesan adhesive layer.

Next, with reference to FIGS. 11A to 11F, a manufacturing method for theresin base materials with single-sided wiring circuits that constitutethe multi-layer wiring board will be described below, in detail.Different from the conventional substrate, the resin base material withsingle-sided wiring circuit of the present embodiment is not limited bythe outer shape (formation position of the partial multi-layersubstrates) of the motherboard, and therefore, the resin base plateswith single-sided wiring circuits that have the same shape or differentshapes can be formed onto the original base plate over a maximum area.

By using a polyimide base material 50 with single-sided copper foil 52placed on one surface of a polyimide base material 51 as shown in FIG.11A as a starting material, the copper foil 52 is etched through asubtractive method so that a base material 53 on which a circuit hasbeen formed as shown in FIG. 11B is prepared. This base material may ofcourse be obtained by using a polyimide base material without copperfoil as a starting material, through an additive method or asemi-additive method.

Next, as shown in FIG. 11C, an adhesive layer 54 is formed on a surfaceof the base material 53 with the circuit formed thereon on the oversideto the copper foil 52 Although a layer made of a thermoplastic polyimideto which a thermo-setting property is imparted is used for the adhesivelayer 54. Adhesive layer 54 may of course be made of a thermosettingresin typically represented by epoxy or a thermoplastic resin such asthermoplastic polyimide.

Here, the three-layer structure of the copper foil 52, the polyimidebase material 51 and the adhesive layer 54 has an asymmetrical structurewith respect to the surface and the rear surface thereof so that it ispreferable to prevent undesired warping from occurring in the succeedingprocesses after the formation of the layering layer. Moreover, theadhesive layer 54 is preferably set to have a glass transitiontemperature of not more than 110° C. and a normal-temperature elasticmodulus of not more than 1300 MPa.

Next, as shown in FIG. 11D, after a hole-forming process (via-holeforming process) has been carried out with a UV-YAG laser beam so as topenetrate the adhesive layer 54 and the polyimide base material 51, adesmear process is carried out by soft etching through plasmairradiation so that the hole 55 is filled with hole-filling-use silverpaste 56 to form an IVH.

Here, when a carbon dioxide laser, by using an excimer laser or thelike, it becomes possible to carry out the processes at higher speeds.Moreover, with respect to the desmear method, a wet desmear processusing permanganate is also generally used.

With respect to the IVH filling conductive paste, in addition to silverpaste, various metal pastes, such as copper paste, carbon paste andnickel paste, may be used.

Next, as shown in FIG. 11E, a press working is applied along a dot lineL using a die so that an outer-shape machining process is carried toform a predetermined shape. Thus, a resin base material 57 withsingle-sided wiring circuit as shown in FIG. 11F is formed through theouter-shape machining process. In this case, in order to prevent the IVHfrom being damaged by the conductive paste 56, it is necessary toprovisionally cure the conductive paste 56 to a degree so as not tocause any damage upon contact. More specifically, the conductive paste56 is preferably cured to have a hardness of not less than 2B on thebasis of pencil hardness. Since the resin base material 57 withsingle-sided wiring circuit of this type can be formed without beinglimited by the outer shape of the motherboard 20, it becomes possible toreduce members to be eliminated.

Referring to FIGS. 12A to 12C, manufacturing methods for variousmulti-layer boards by using the resin base material 57 with single-sidedwiring circuit and the motherboard produced through the above-mentionedmanufacturing processes will be described below.

As shown in FIG. 12A, a motherboard FPC 60 has a wiring circuit 61formed thereon and is provided with a cover layer 62 with an opening(opening portion 62A) formed at a portion to receive laminated layersbeing formed on the surface thereof. Two resin base materials 57 withsingle-sided wiring circuit having conductive paste 56 and being formedinto a predetermined shape are positioned to electrically conduct theconductor layer of the motherboard or the conductor layer of the resinbase material 57 with single-sided wiring circuit one another, and thensuperposed one another.

Thereafter, these members are subjected to heating and pressingprocesses with a vacuum heat pressing machine under a degree of vacuumof not more than 1 kPa so that a substrate 63 containing a Iti-1a erportion 64 as shown in FIG. 12B is formed.

Here, upon carrying out the batch laminating processes, the resin basematerials 57 with single-sided wiring circuits have an outer shape thathas been formed into a predetermined shape may be laminated on themotherboard sheet by sheet, or after a plurality of the resin basematerials 57 with single-sided wiring circuits have been preliminarilylaminated, the laminated substrates may be placed on the motherboardthrough the batch process.

The positioning process may be carried out through a pin alignmentmethod or an image recognition method. However, since the pin alignmentmethod requires a space used for forming a pin hole, the positioningprocess using the image recognition is preferably adopted.

Next, as shown in FIG. 12C, solder resist 65 is applied onto thesubstrate 63 so as to cover a gap between the cover layer 62 and themulti-layer portion 64 of the motherboard FPC 60 as well as one portionof the surface of the multi-layer portion 64 and one portion of thesurface of the cover layer 62, by using a print method, and then curedto form a multi-layer wiring board 66 First Embodiment-First ModifiedEmbodiment.

With reference to FIGS. 13A and 13B, a manufacturing method for amulti-layer wiring board in accordance with a first modified embodimentof the first embodiment will be described below. Here, in FIG. 13, thoseparts corresponding to those shown in FIG. 12 are indicated by the samereference numerals as those of FIG. 12, and the description thereof isomitted.

As shown in FIG. 13A, a motherboard FPC 60 has a wiring circuit 61formed thereon, two resin base materials 57 and 70 with single-sidedwiring circuits having conductive paste 56 that have been manufacturedby the same method as shown in FIG. 11 are positioned to electricallyconnect the conductor layer of the motherboard or the conductor layer ofthe resin base material 57 with single-sided wiring circuit one another,and then superposed thereon. The resin base material 70 with asingle-sided wiring circuit, which is made in contact with the circuitface of the motherboard FPC 60, has such an outer shape that itsinsulating layer (polyimide base material 51) is allowed to cover aportion to be covered with the cover layer, such as the copper foilportion of the motherboard FPC 60. Thus, the insulating layer of theresin base material 70 is also performed as the cover layer.

With respect to the positioning process in the modified example also,the positioning process using the image recognition is preferablyadopted.

After the positioning process, these members are subjected to heatingand pressing processes by a vacuum heat pressing machine under a degreeof vacuum of not more than 1 kPa so that a substrate 71 as shown in FIG.13B is formed. In accordance with this method, upon heat pressing, astep difference is formed between the resin base materials 57 and 70with single-sided wiring circuits so that it is preferable to prepare acushioning structure for compensating for the step difference.

First Embodiment-Second Modified Embodiment

Referring to FIGS. 14A to 14E, a manufacturing method for a multi-layerwiring board in accordance with a second modified embodiment of thefirst embodiment will be described below. Here, in FIG. 14 also, thoseparts corresponding to those shown in FIG. 12 are indicated by the samereference numerals as those of FIG. 12 and the description thereof isomitted.

As shown in FIG. 14A, a motherboard FPC 60 has a wiring circuit 61formed thereon and is provided with a cover layer 62 with openings(opening sections 62A and 62B) formed at portions to receive laminatedlayers that is formed on the surface thereof. Two layers of resin basematerials 57 with single-sided wiring circuits that have an outer shapethat has been formed into a predetermined shape, as shown in FIG. 9, arepositioned, and then superposed thereon. Thereafter, these members aresubjected to heating and pressing processes by a vacuum heat pressingmachine under a degree of vacuum of not more than 1 kPa so that a firstmulti-layer portion 64 as shown in FIG. 14B is formed.

As shown in FIG. 14C, onto the other opening section 62B of themotherboard FPC 60, three layers of resin base materials 57 withsingle-sided wiring circuits that have an outer shape that has beenformed into a predetermined shape are positioned accordingly, and thensuperposed thereon. Thereafter, these members are subjected to heatingand pressing processes by a vacuum heat pressing machine under a degreeof vacuum of not more than 1 kPa so that a second multi-layer portion 67as shown in FIG. 14D is formed.

Next, as shown in FIG. 14E, solder resist 65 is applied thereto so as tocover gaps between the cover layer 62 and the multi-layer portions 64,67 of the motherboard FPC 60 as well as one portion of the surface ofeach of the multi-layer portions 64, 67 and one portion of the surfaceof the cover layer 62, by using a print method, and then cured to form amulti-layer wiring board 68.

In this manner, in accordance with the manufacturing method for themulti-layer substrate of the first embodiment, it is possible to form acircuit that has a multi-layer portion having a desired thickness at adesired position. Here, with respect to the resin base material withsingle-sided wiring circuit, those having a conductor layer with athickness of approximately 8 to 18 μm and an insulating base materialwith a thickness of 25 to 100 μm are generally used.

Second Embodiment

With reference to attached Figures, a second embodiment of the presentinvention will be described below.

FIGS. 15 and 16 show a second embodiment of a multi-layer wiring boardin accordance with the present invention.

In the multi-layer wiring board of the present embodiment, at aplurality of portions on the surface and rear surface of a motherboard(base material) 210, partial wiring boards (multi-layer portions) 220,which have outer shapes that have been preliminarily formed intopredetermined shapes, are bonded so as to form an island shape. Here,the island shape is defined as a state in which the peripheral sides ofthe partial wiring boards 220 are not coincident with the peripheralsides of the motherboard 210 so that the partial wiring boards 220 areplaced inside the area determined by the peripheral sides of themotherboard 210. Here, the predetermined shapes are determined byrequirements in designing the motherboard.

The partial wiring boards 220 are formed as follows: a plurality ofresin base materials 221A, 221B and 221C with single-sided wiringcircuits accordingly, which have outer shapes that have been formed intopredetermined shapes that are smaller than the outer shape of themotherboard 210, are laminated on the surface and rear surface of themotherboard 210 in succession through a batch process.

As shown in FIG. 15, the resin base materials 221A, 221B and 221C havebeen formed into predetermined shapes so as to have decreasing its areasin succession, and therefore, when superposed one after another, thelaminated resin substrates 221A, 221B and 221C virtually have a pyramidshape in the cross-section thereof.

In other words, the following relationship is satisfied: (area of resinbase material 221A)>(area of resin base material 221B)>(area of resinbase material 221C). More specifically, as shown in FIG. 16, when viewedfrom the normal line of the plane of the motherboard printed substrate220, the outer shape of the resin base material 221B or the outsidecontour thereof is located inside the outer shape of the resin basematerial 221A or the outside contour thereof, and the outer shape of theresin base material 221C or the outside contour thereof is locatedinside the outer shape of the resin base material 221B or the outsidecontour thereof. In other words, those shapes are formed in such amanner that, when the centers of gravity of the respective resin basematerials 221A, 221B and 221C are made coincident with one another, theouter sides 229 of the resin base material 221A are not coincident witheach other. In the same manner, as shown in FIG. 16, when the centers ofgravity of the respective resin base materials 221A, 221B and 221C aremade coincident with one another, the outer sides 229 of the resinsubstrate 221A are not made coincident with the outer sides 219 of themotherboard 10.

The motherboard 210 is provided with conductor layers (wiring circuits)212 formed on the surface and rear surface of an insulating basematerial 211. The insulating base material 211 of the motherboard 210 ismade from a flexible resin such as polyimide. Additionally, with respectto the flexible resin, other materials, such as liquid crystal polymer(LCP), polyether imide (PEI), polyether ether ketone (PEEK),polyethylene naphthalate (PEN), polyethylene terephthalate (PET) andpolyether sulfone (PES), may be used. Each of the resin base materials221A, 221B and 221C with respective single-sided wiring circuits isprovided with a conductor layer (wiring circuit) 223 formed on onesurface of an insulating base material 222. The insulating base material222 of each of the resin base materials 221 with single-sided wiringcircuits may also be made from a flexible resin such as polyimide. Theinsulating base material 211 of the motherboard 210 and the insulatingbase material 223 of each of the resin base materials 221A, 221B and221C with single-sided wiring circuits are preferably made from the samematerial such as polyimide from the viewpoints of thermal and mechanicalinfluences.

The conductor layers 223 of the resin base materials 221A, 221B and 221Cwith single-sided wiring circuits, as well as the conductor layers 223of the resin base materials 221 with single-sided wiring circuits andthe conductor layer 212 of the motherboard 210, are electricallyconnected to each other by conductive paste 225 being filled in innervia holes (via holes) 224 respectively formed in the resin basematerials 221 with respective single-sided wiring circuits.

This multi-layer wiring board in accordance with the second embodimentis manufactured by layering the resin base materials 221A, 221B and 221Cwith single-sided wiring circuits that have outer shapes that have beenformed into predetermined shapes to one portion of the surface and/orthe rear surface of the motherboard 210. More specifically, a build-upmethod in which the resin base materials 221 with single-sided wiringcircuits are bonded to one after another sheet by sheet or acolamination method may be used. Here, the colamination method, whichhas an arrangement in which the resin base materials 221A, 221B and 221Cwith respective single-sided wiring circuits, each of which has a wiringcircuit and a via hole formed thereon, and has an outer shape that hasbeen formed into a predetermined shape, are superposed on one portion ofthe surface and/or the rear surface of the motherboard 210, and bondedto one after another by heating and pressing these through a batchprocess, is more preferably used since it is a simpler method and can beachieved at low costs. Additionally, the batch laminating process can beexecuted, after resin base materials with single-sided wiring circuitshaving an outer shape that has been formed into a predetermined shapehave been laminated on the motherboard sheet by sheet, or it can beexecuted after a plurality of the resin base materials with single-sidedwiring circuits have been preliminarily laminated, and placed on themotherboard.

The mutual layering processes between the resin base materials 221A,221B and 221C with single-sided wiring circuits and the layeringprocesses between the resin base materials 221A, 221B and 221C withsingle-sided wiring circuits and the motherboard 210 can be carried outby forming a layering layer (not shown) on a surface on the sideopposite to the conductor layer 223 of the insulating base material 222of each of the resin base materials 221A, 221B and 221C withsingle-sided wiring circuits and by using this layering layer.

In the case when the insulating base material 222 of each of the resinbase materials 221A, 221B and 221C with single-sided wiring circuits ismade from a material having an adhesive property, such as thermoplasticpolyimide, thermoplastic polyimide to which a thermosetting property isimparted or liquid crystal polymer, the above-mentioned layering layercan be omitted.

With these arrangements, electronic-component-packaging-usemulti-layer-forming portions (partial wiring boards 220) can be freelyplaced on desired positions on the surface of the motherboard 210, andit becomes possible to reduce excessive multi-layer-forming portions,and consequently to greatly cut the material costs.

In particular, in the case when the electronic-part packaging portionsare made from an expensive material such as polyimide in response torequirements such as better dielectric properties, light weight andthinness, the above-mentioned arrangements exert greater effects.

Moreover, in the above-mentioned substrate structures, the insulatinglayer (insulating base material 222) of the partial wiring board 220performing as an electronic part packaging portion and the insulatinglayer (insulating base material 211) of a flex portion (motherboard 210)are preferably made from the same material so that the thermal andmechanical properties of the two layers are made coincident with eachother, and therefore, it becomes possible to provide high reliability inthermal and mechanical properties.

In this arrangement, the resin base materials 221A, 221B and 221C withsingle-sided wiring circuits that have been laminated on the motherboard10 have a pyramid shape, and therefore, when the motherboard 210 is bentas schematically shown in FIG. 17, portions S, which are subject tostress, and located between the motherboard 210 and the resin basematerial 221A with single-sided wiring circuit as well as between thelaminated resin base materials 221A, 221B and 221C with single-sidedwiring circuits, are dispersed.

With this arrangement, stress concentration is alleviated so that theanti-separation strength (peel strength) is improved, thereby making itpossible to provide a multi-layer wiring board having high anti-bendingstrength. In particular, a superior bending property, which is a featureof the multi-layer flexible printed wiring board (FPC), is properlyexerted so that the features of the multi-layer flexible printed wiringboard are exerted to the maximum.

Next, referring to FIGS. 18A to 18F, a manufacturing method for theresin base material with single-sided wiring circuit that forms themulti-layer wiring board of the above-mentioned second embodiment willbe described below. Different from the conventional substrate, the resinbase material with single-sided wiring circuit in accordance with thepresent embodiment, which is not limited by the outer shape (formationposition of the partial Iti-1a er substrates) of the motherboard, andmakes it possible to assemble the resin base plates with single-sidedwiring circuits that have the same shape or different shapes onto thebase original plate over a maximum area.

By using a polyimide base material 250 having single-sided copper foil252 placed on one surface of a polyimide base material 251 as shown inFIG. 18A as a starting material. The copper foil 252 is etched through asubtractive method so that a base material 260 having a circuit portion253 formed thereon as shown in FIG. 18B is prepared. This base materialmay also be obtained by using a polyimide base material without copperfoil as a starting material, through an additive method or asemi-additive method.

Next, as shown in FIG. 18C, an adhesive layer 254 is formed on a surfaceof the base material 260 with the circuit formed thereon on the oversideof the circuit portion 253. With respect to the adhesive layer 254, amaterial prepared by imparting a thermosetting property to athermoplastic polyimide a thermosetting resin typically represented byepoxy or a thermoplastic resin, such as thermoplastic polyimide, may beused.

Here, the three-layer structure of the circuit portion (copper foil)253, the polyimide base material 251 and the adhesive layer 254 has anasymmetrical structure with respect to the surface and the rear surfacethereof so that it is preferable to prevent undesired warping fromoccurring in the succeeding processes after the formation of thelayering layer. Moreover, the adhesive layer 254 is preferably set tohave a glass transition temperature of not more than 110° C. and anormal-temperature elastic modulus of not more than 1300 MPa.

Next, as shown in FIG. 18D, after a hole-forming process (via-holeforming process) has been carried out with a UV-YAG laser beam so as topenetrate the adhesive layer 254 and the polyimide base material 251, adesmear process is carried out by soft etching through plasmairradiation so that the hole (via hole) 55 is filled withhole-filling-use silver paste 56 to form an NH.

Here, by using a carbon dioxide laser, an excimer laser or the like, itbecomes possible to carry out the processes at higher speeds. Moreover,with respect to the desmear method, a wet desmear process usingpermanganate is also generally used With respect to the IVH fillingconductive paste, in addition to silver paste, various metal pastes,such as copper paste, carbon paste and nickel paste, may be used.

After filling the conductive paste, the conductive paste 256 isprovisionally cured at 60° C. to 140° C. for 0.5 to 2 hours. Thus, theconductive paste 256 is cured to have a hardness of not less than 2B onthe basis of pencil hardness, thereby making it possible to preventcoming off or deformation of the paste during a die-releasing process ora packaging process, which will be described later.

Next, as shown in FIG. 18E, a die pressing process is applied along adot line L so that an outer-shape machining process is carried to form apredetermined shape, thus, three resin base materials 261A, 261B and261C with single-sided wiring circuits, which have respectivelydifferent sizes (areas) that vary step by step as shown in FIG. 18F, areformed. More specifically, the respective resin base materials 261A,261B and 261C are designed so that the outer shape of the second basematerial 261B (or 261C) bonded to the first base material is locatedinside the outer shape of the first base material 261A (or 261B) on themotherboard side.

With reference to FIGS. 19A to 19C, manufacturing methods (laminatingmethods) for the multi-layer wiring boards of the embodiment 2 by usingthe base material produced as described above will be described below.

As shown in FIG. 19A, a motherboard FPC 270 has wiring circuits 272formed on both of the surfaces of a flexible insulating base material271 and is provided with a cover layer 273 with an opening (openingsection 273A) formed at a portion to receive laminated layers that isformed on the surface thereof, resin base materials 261A, 261B and 261Cwith single-sided wiring circuits, which have outer shapes that havebeen formed into predetermined shapes, are positioned in succession, andsuperposed into a pyramid shape.

Next, a batch pressing process is carried out on the motherboard FPC270, the resin base materials 261A, 261B and 261C by a vacuum heatpressing machine under a degree of vacuum of not more than 1 kPa so thata substrate containing a multi-layer portion 280 as shown in FIG. 19B isformed. Moreover, simultaneously with the batch pressing process, themotherboard FPC 270, the resin base materials 261A, 261B and 261C areheated in the range of 150° C. to 190° C. for about one hour to carryout a main curing process on the conductive paste. Thus, it becomespossible to provide efficient operations, and also to prevent resindeterioration in the lower-layer portion due to repeated heatingprocesses.

Upon positioning the respective resin base materials 261A, 261B and261C, rather than adopting a pin-alignment method that requires a spaceused for forming a pin hole, a positioning process using imagerecognition is more preferably adopted.

Next, as shown in FIG. 19C, solder resist 274 is applied by using aprint method in a manner so as to cover a gap between the cover layer273 of the motherboard FPC 270 and the multi-layer portion 280 as wellas one portion of the surface of the multi-layer portion 280 and oneportion of the surface of the cover layer 273, and cured thereon to forma multi-layer wiring board 290.

By repeating the processes shown in FIGS. 1 9A to 19C, theaforementioned multi-layer wiring board shown in FIG. 15 is formed.

The multi-layer wiring board in accordance with the second embodimenthas at least features described below:

(1) The multi-layer wiring board is provided with a motherboard 210having a first surface, a first base material 221A with single-sidedwiring circuit, which is bonded to the first surface, and has an outershape that has been formed into a predetermined shape and a second basematerial 221B with single-sided wiring circuit, which is bonded to thesurface of the first base material, and has an outer shape that has beenformed into a predetermined shape, and in this arrangement, the firstbase material is provided with a first inner via hole 225 thatelectrically connects a wiring on the motherboard to a wiring on thefirst base material, and the second base material is provided with asecond inner via hole 225 that electrically connects a wiring on thefirst base material to a wiring on the second base material, and whenviewed from the direction of the normal line of the motherboard, theouter shape 229 of the second base material 221B bonded to the surfaceof the first base material is located inside the outer shape 229 of thefirst base material 221A bonded to the first surface of the wiringboard.

(2) When viewed from the direction of the normal line of themotherboard, the outer shape 229 of the third base material 221C bondedto the surface of the second base material is located inside the outershape 229 of the second base material 221B.

(3) A first base material peripheral edge line 229 that determines theperipheral edge of the rear surface of the first base material bonded tothe first surface of the motherboard is located inside a motherboardprint peripheral edge line 229 that determines the peripheral edge ofthe motherboard, without contacting the corresponding line.

Third Embodiment

FIGS. 20 and 21 show a multi-layer wiring board in accordance with athird embodiment. This multi-layer wiring board is characterized byhaving a motherboard 310 and partial multi-layer wiring boards(multi-layer portions) 320A, 320B, 320C and 320D that have island shapesand respectively laminated at a plurality of portions on the surface andrear surface of the motherboard printed substrate 310. Here, the islandshape is defined as a state in which the peripheral sides of the partialwiring boards 320A to 320D are not coincident with the peripheral sidesof the motherboard 310 so that the partial wiring boards 320A to 320Bare placed inside the area determined by the peripheral sides of themotherboard 310. Here, the predetermined shapes are determined byrequirements in designing the motherboard.

The partial multi-layer wiring boards 320A, 320B, 320C and 320D areformed as follows: a plurality of single-sided circuit board formulti-layer wiring boards 330, which have outer shapes that have beenformed into predetermined shapes that are smaller than the outer shapeof the motherboard 310, are laminated on the surface and rear surface ofthe motherboard 310 by a batch process. In the present embodiment, eachof the partial multi-layer wiring boards 320A, 320B, 320C and 320D has atwo-layer structure.

Each of the single-sided circuit board for multi-layer wiring boards 330has an insulating base material 331, a conductive pattern 332 formed onone surface of the insulating base material 331, a layering layer 333bonded to the other surface of the insulating base material 331 and aninterlayer conductive portion 334 prepared as an inner via hole formedin a manner so as to penetrate the insulating base material 331 and thelayering layer 333.

The single-sided circuit board for multi-layer wiring board 330 may beprepared as either a rigid printed wiring board made from a materialsuch as a phenol-based resin and an epoxy-based resin, or a flexibleprinted wiring board made from a material such as a polyester-basedresin and a polyimide-based resin. Here, in the case when the insulatingsubstrate 331 of the single-sided circuit board for multi-layer wiringboard 330 has an interlayer layering property, the layering layer 333may be omitted.

Among the single-sided circuit board for multi-layer wiring boards 330of the partial multi-layer wiring boards 320A, 320B, 320C and 320D, thesurface of the single-sided circuit board for multi-layer wiring board330 performing as the outermost layer is coated with solder resist 335.

The single-sided circuit board for multi-layer wiring board 330performing as the outermost layer of each of the partial multi-layerwiring boards 320A, 320B, 320C and 320D is provided with an electronicpart 350 packaged thereon through a bump 351. Thus, it is possible toprovide a double-sided multi-layer/double-sided packaging circuitsubstrate.

The motherboard 310 is prepared as a main single-sided circuit substratehaving a conductive pattern 312 formed on one surface of an insulatingbase material 311. In he motherboard 310, at least one portion (twoportions in this embodiment) of the insulating base material 311 ispartially removed with the rear surface of the conductive pattern 312being exposed at the removed portion 319 of the insulating base material311. Further, on the other face side (rear face side) of the insulatingse material 311, the single-sided circuit board for multi-layer wiringboards 330 of partial multi-layer wiring boards 320C and 320D arelaminated in a manner so as to be conduction-connected to a rear-surfaceexposure portion 312B of the conductive pattern 312 to form the partialmulti-layer wiring boards 320C and 320D.

Here the single-sided circuit board for multi layer wiring boards 330 ofthe partial multi-layer wiring boards 320A and 320B are laminated on onesurface (surface) of the insulating base material 311 in a manner so asto be electrically connected to a surface exposure portion 312A of theconductive pattern 312 to form the partial multi-layer wiring boards320A and 320B.

The motherboard 310 may also be prepared as either a rigid printedwiring board made from a material such as phenol-based resin and anepoxy-based resin, or a flexible printed wiring board made from amaterial such as a polyester-based resin and a polyimide-based resin.

The surface of the motherboard 310 is coated with a cover layer 318.Moreover, a gap portion between the cover layer 318 and the partialmulti-layer wiring boards 320A and 320B is filled with solder resist 317applied thereto.

With reference to FIGS. 22 to 25, a manufacturing method of circuitssubstrates constituting a multi-layer wiring board in accordance withthe present embodiment described above will be described below.

FIGS. 22A to 22E show manufacturing processes of the motherboard 310. Asshown in FIG. 22A, a general-use single-sided copper coat polyimide basematerial (single-sided conductor coat lamination plate) 360 is used as astarting material. The single-sided copper coat polyimide base material360 is a single-sided copper coat lamination plate (CCL) having copperfoil 3 16 placed as a conductor layer on only one of the surfaces of theinsulating base material 311 made of a polyimide film.

Here, polyimide is selected as the insulating base material from theviewpoints of heat resistance and dielectric properties of thesubstrate, and other substrates such as a steel coat phenol substrate, acopper coat paper epoxy substrate, a steel coat paper polyestersubstrate, a copper coat glass epoxy substrate and a copper coat glasspolyimide substrate, composed of a base material made from basematerial, such as glass cloth, glass mat and synthetic fibers, and athermosetting resin, may be used. Moreover, with respect to a structurein which no base material is combined, a copper coat polyestersubstrate, a copper coat polyether imide substrate and a copper coatliquid crystal polymer substrate may be used.

First, in a conductive pattern forming process, etching resist islaminated on a copper foil 316 of the single-sided copper coat polyimidebase material 360, and this is subjected to exposure to form a wiringpattern thereon, and then developed. Thereafter, the exposed copper isetched through a cupric chloride bath to form a conductive pattern 312.Subsequently, the etching resist is removed so that a single-sidedcircuit substrate 361, shown in FIG. 22B, is formed.

As shown in FIG. 22C, on the surface (upper surface) of the single-sidedcircuit substrate 361, a cover layer 318, which has a portion(surface-side multi-layer portion) 314 for receiving laminatedsingle-sided circuit board for multi-layer wiring boards 330preliminarily formed therein as an opening, is placed in order toprotect the conductive pattern 312. With respect to the material for thecover layer 318, solder resist and the like may be used.

Next, in an insulating base material removing process, as shown in FIG.22D, etching resist 362 is laminated on both of the surfaces of thesingle-sided circuit substrate 361, and the copper foil side (surfaceside) is entirely subjected to exposure, and the polyimide side (rearsurface side) is subjected to exposure to form an opening pattern, andthen developed.

Thereafter, the insulating base material 311 made from polyimide isetched by using oxygen plasma or a strong alkali aqueous solution. Uponcompletion of the etching, the etching resist 362 is removed. Thus, asshown in FIG. 22E, the insulating base material 311 of the single-sidedcircuit substrate 361 is partially removed over a predetermined area sothat a motherboard 310 in which the rear surface 3 12B of the conductivepattern 312 is exposed to the removed portion (rear-surface-sidemulti-layer portion) 319 of the insulating substrate 311 is formed.

Additionally, the insulating base material removing process for formingthe removed portion 319 in the insulating base material 311 may also becarried out by a laser process which applies a laser beam from the rearsurface side of the insulating base material 311.

FIG. 23 is a schematic plan view that shows the motherboard 310, andFIG. 22E is a cross-sectional view taken along line XXII-XXII in FIG.23.

With reference to FIGS. 24A to 24F, manufacturing processes of a inle-sided circuit board for multi-layer wiring board 330 in accordancewith the present embodiment will be described below. As shown in FIG.24A, a general-use single-sided copper coat polyimide base material(single-sided conductor coat lamination plate) 370 is prepared as astarting material.

The single-sided copper coat polyimide base material 370, which is thesame as the single-sided copper coat polyimide base material 360 for usein the motherboard 310, is a single-sided copper coat lamination plate(CCL) having copper foil 336 placed as a conductor layer on only one ofthe surfaces of the insulating base material 331 made of a polyimidefilm.

Here, the insulating base material 311 of the motherboard 310 and theinsulating base material 331 of the single-sided circuit board formulti-layer wiring board 330 are preferably made from the same materialfrom the viewpoints of thermal and mechanical properties.

First, as shown in FIG. 24B, the copper foil 336 of the single-sidedcopper coat polyimide base material 370 is etched in the same manner asthe forming process of the motherboard to form a conductive pattern 332.

Subsequently, as shown in FIG. 24C, thermoplastic polyimide is joined tothe surface of the insulating base material 331 on the side opposite tothe conductive pattern 332 by using a heat pressing machine to form alayering layer 333. With respect to the layering layer 333, othermaterials, such as phenolic resin, phenoxy resin, polyimide resin andxylene resin, or mixed resin of two of more kinds of these, polyetherimide resin, liquid crystal polymer and polyamide resin, may be used.

Next, as shown in FIG. 24D, a laser beam is applied from the layeringlayer 333 side to a desired position to be used for interlayerconnection, to penetrate the insulating base material 331 and thelayering layer 333, thereby forming a hole (via hole) 337 that contactsthe copper foil (conductive pattern 332).

Subsequently, as shown in FIG. 24E, thermosetting silver paste isembedded and injected into the hole 337 through a print method or thelike to form an interlayer conductive portion 334. With respect to theconductive paste to be injected into the hole 37, materials, such asgold, copper, nickel or carbon powder, or a conductive compositionprepared by mixing alloy powder or mixed powder of these and a bindercomponent such as phenolic resin, polyester resin, epoxy resin andpolyimide resin, can be used.

Here, with respect to the printing/injecting process of the conductivepaste, a print method using a metal mask, a print method using a maskingfilm and an injecting method using a dispenser can be used.

Subsequently, the lamination base material 371 on which the silver pastehas been printed is heated in an oven so that the silver paste is dried.

The lamination base material 371 is pressed by using a die to form anouter shape thereof that is smaller than the outer shape of themotherboard 310 as indicated by dot line C. Thus, as shown in FIG. 24F,a single-sided circuit board for multi-layer wiring boards 330 having adesired size is prepared. In this outer-shape forming process, in orderto allow the single-sided circuit board for multi-layer wiring board 30to enter the surface side multi-layer portion (opening portion) 314 ofthe cover layer 318 and the removed portion 3 19 of the insulating basematerial (opening portion) 3 11, the size thereof is set to virtuallythe same size of these openings or a size slightly smaller than theseopenings.

Next, referring to FIGS. 25A to 25C, laminating processes of themotherboard 310 and the single-sided circuit board for multi-layerwiring board 330 that are formed through the above-mentionedmanufacturing processes will be described below. A plurality of thesingle-sided circuit board for multi-layer wiring boards 330,manufactured through the above-mentioned processes, are prepared. Asshown in FIG. 25A, a predetermined number of the single-sided circuitboard for multi-layer wiring boards 330 are respectively positioned onthe surface-side multi-layer portions 314 on the conductive pattern 3 12side (surface side) of the motherboard 310 and the respective removedportions 3 19 on the rear-surface side of the insulating base material 311. After the completion of the positioning processes, the respectivemembers are superposed, and heated and pressed by a vacuum pressingmachine so that a double-sided lamination circuit substrate 380, asshown in FIG. 25B, is formed.

With respect to the positioning processes, rather than adopting apin-alignment method that requires a space used for forming a pin hole,a positioning process using image recognition is more preferablyadopted.

Next, as shown in FIG. 25C, pieces of solder resist 317 and 335 areapplied by using a print method in a manner so as to cover a gap betweenthe cover layer 318 of the motherboard 3 10 and the multi-layer portionas well as one portion of the surface of the multi-layer portion, andcured thereon.

Lastly, the conductive pattern 332, exposed so as to package anelectronic part, is coated with noble metal 338 such as gold to form amulti-layer wiring board that allows double-sided packaging processes.

The above-mentioned circuit substrate has the following features andeffects.

(1) By solving the problem that, when the single-sided wiring board isused as a motherboard, double-sided multi-layer forming processes anddouble-sided packaging processes are not available, the single-sidedwiring board can be used as the motherboard 310, that is, the mainsingle-sided circuit substrate. Therefore, different from the case usingthe double-sided circuit substrate, it is not necessary to remove mostof the conductor layer on one surface upon formation of the conductivepattern, thereby making it possible to reduce wasteful use of materialsand resources. Moreover, it is not necessary to provide complexmanufacturing processes for forming through holes and the like.

(2) The single-sided wiring board is used as the motherboard 310.Therefore, in the case when the motherboard 310 is a flexible substrate,portions having no multi-layer structure are allowed to have a highbending property so that it is possible to provide a high-densitydouble-sided partial multi-layer wiring board having a superior bendingproperty.

(3) With respect to the partial multi-layer wiring board, that is, thein single-sided circuit board for multi-layer wiring board 330, thosesubstrates that are formed to have outer shapes corresponding to thesizes of the partial multi-layer wiring portions are used. Therefore, incomparison with a case in which: those substrates corresponding to thepartial multi-layer wiring portions are also prepared to have the samesize as that of the motherboard 310, and upon forming the outer shape ofthe motherboard 310, each substrate is punched out to have the sameouter shape as the motherboard 310, it is possible to reduce thequantity of materials for the multi-layer wiring board-use one-sidecircuit substrate 330, and consequently to cut wasteful use ofmaterials.

Not limited to the above-mentioned double-sided lamination substrate,the circuit substrate of the present invention may have an arrangementin which as shown in FIG. 26, a flip-chip-type electronic part 350 maybe directly packaged onto the conductive pattern 312 of the motherboard310 and the removed portion 3 19 of the insulating base material 311.The packaging process of the electronic part 350 onto the removedportion 319 of the insulating base material 311 is carried out whilebeing conduction-connected to the rear-face exposed portion 312B of theconductive pattern 312.

Fourth Embodiment

With reference to Figures, the following description will discuss afourth embodiment of the present invention. FIGS. 27 and 28 show thefourth embodiment of a multi-layer wiring board in accordance with thepresent invention. This multi-layer wiring board is provided with arelay board 410 such as a motherboard wiring board and partialmulti-layer portions 420A and 420B formed by respectively laminatingpartial multi-layer substrates 430 at specific portions on the surfaceand rear surface of the relay board 410.

The relay board 410 is constituted by a base material with single-sidedwiring circuit that is provided with a conductor layer (including aconductor land portion) 412 forming a wiring pattern, which is formed onone surface (upper surface 410A) of an insulating base material 411 thatis compatibly used as an adhesive layer. With respect to the materialfor the insulating base material 411 compatibly used as the adhesivelayer, thermosetting polyimide, thermoplastic polyimide, thermoplasticpolyimide to which a thermosetting property is imparted, liquid crystalpolymer, epoxy resin and the like can be used.

On the conductor layer surface (upper surface 410A) forming the wiringpattern of the insulating board 411, an insulating resin layer 413,which also performs as an adhesive layer, is formed. The insulatingresin layer 413 and the insulating board 411 may be made of the samematerial.

With respect to the relay board 410, interlayer conductive portions 415and 417 formed by via holes 414 and 416 are respectively formed in theinsulating base material 411 and the insulating resin layer 413. Theinterlayer conductive portions 415 and 417 are constituted by the viaholes 414 and 416 in which conductive paste is embedded and injected.

On the surface of the insulating base material 411 on the side oppositeto the conductor layer surface, that is, the rear surface 410B, and thesurface (upper surface 413A) of the insulating resin layer 413, wiringboard for partial multi-layers 430 having outer shapes that have beenpreliminarily formed into a predetermined shape are laminated inconductive-association with the conductor layer 412 forming the wiringpattern of the relay board 410 through the interlayer conductive portion415 or 417.

In the same manner as the relay board 410, the wiring board for partialmulti-layer 430 is also constituted by a base material with single-sidedwiring circuit that is provided with a conductor layer (including aconductor land portion) 432 forming a wiring pattern, which is formed onone surface of an insulating base material 431 that is compatibly usedas an adhesive layer. With respect to the wiring board for partialmulti-layer 430, an interlayer conductive portion 434 is formed in theinsulating base material 431 through a via hole 433. The interlayerconductive portion 434 is also constituted by the via hole 433 in whichconductive paste is embedded and injected.

With respect to the wiring board for partial multi-layer 430, on theupper surface 410A side of the relay board 410, that is, on the partialmulti-layer portion 420A, a plurality of them are laminated with theconductor layer 432 forming a wiring pattern facing down, and on therear-surface 410B side of the relay board 410, that is, on the partialmulti-layer portion 420B, a plurality of them are laminated with theconductor layer 432 forming a wiring pattern facing up, thus, theselayers are bonded by the insulating base material 411, the insulatingresin layer 413 or the insulating base material 431, which serve asadhesive layers between layers. In other words, the wiring board forpartial multi-layers 430 are laminated on the upper side and the lowerside of the relay board 410 with the conductor layer 432 side thereofforming a wiring pattern facing the relay board 410 side.

On the surface 430A of the insulating base material 43 1 of the wiringboard for partial multi-layer 430 that forms the outermost layer of eachof the partial multi-layer portions 420A and 420B, a conductor layer 435forming a wiring pattern and a component-packaging-use conductor landportion 436 are formed.

With the above-mentioned structure, even when a lamination materialhaving a conductor layer such as copper foil formed on only one surfaceof the insulating base material 411 is used as a starting material, apartial multi-layer structure is prepared at desired portions on both ofthe surface and rear surface of the relay board 410, thereby allowingdouble-sided packaging processes. Moreover, by using the wiring boardfor partial multi-layer 430 having an outer shape that has beenpreliminarily formed into a predetermined shape, it becomes possible toeliminate the necessity of preparing excessive multi-layer portions, andconsequently to cut the number of processes and the material costs.

With reference to FIGS. 29A to 3 1, a manufacturing method for asubstrate with a circuit that is used for a multi-layer wiring board inaccordance with the present embodiment will be described below.

FIGS. 29A to 29E show manufacturing processes of a relay board 410. Asshown in FIG. 29A, a general-use single-sided copper coat polyimide basematerial (single-sided conductor coat lamination plate) 450 is used as astarting material. The single-sided copper coat polyimide base material450 is a single-sided copper coat lamination plate (CCL) having copperfoil 451 placed as a conductor layer on only one of the surfaces of theinsulating base material 411 made of a polyimide film that exerts alayering property when heated. Here, a lamination plate in which apolyimide base material without copper foil is used as a startingmaterial and a conductor layer is formed through an additive method or asemi-additive method may also be used.

First, etching resist is laminated on the copper foil 451 of thesingle-sided copper coat polyimide base material 450, and this issubjected to exposure to form a wiring pattern thereon, and thendeveloped. Thereafter, the exposed copper is etched through a cupricchloride bath to form a conductor layer (conductive pattern) 412.Subsequently, the etching resist is removed so that a substrate withsingle-sided circuit 452, shown in FIG. 29B, is formed.

Subsequently, as shown in FIG. 29C, an insulating resin layer 413, whichalso performs as an adhesive layer, is formed on the conductor layersurface (upper surface 410A) being formed as a wiring pattern of theinsulating base material 411. The insulating resin layer 413 may beformed by a polyimide film that is the same material as the insulatingbase material 411, thus, by using the film-shaped material, a layeringprocess can be carried out on the upper surface 410A of the insulatingbase material 411 by using a contact-layering process, a laminatingprocess or a vacuum laminating process through heat pressing or vacuumheat pressing. Moreover, the insulating resin layer 413 may also beformed through a coating process such as a curtain coating process and aspin coating process by using a precursor varnish of a resin material.

Subsequently, as shown in FIG. 29D, a UV-YAG laser beam, a carbondioxide laser beam or the like is applied to a desired position to beused for interlayer connection from the insulating base material 411side to form a via hole 414 that penetrates the insulating base material11 to contact the rear surface of copper foil (conductor layer 412forming a wiring pattern). Moreover, a UV-YAG laser beam, a carbondioxide laser beam or the like is applied to a desired position to beused for interlayer connection from the insulating resin layer 413 sideto form a via hole 416 that penetrates the insulating resin layer 413 tocontact the upper surface of copper foil (conductor layer 412 forming awiring pattern).

With respect to the hole-forming processes, besides the laser processes,the via holes 414 and 416 may be formed by forming etching resist havinga pattern on the insulating base material 411 and the insulating resinlayer 413 and by etching the insulating base material 411 and theinsulating resin layer 413.

Subsequently, as shown in FIG. 29E, pieces of thermosetting silver paste418 and 419 are embedded and injected into the via holes 414, 416 asconductive paste through a print method or the like to form interlayerconductive portions 415, 417. Thus, a relay board 410 is formed. Here,with respect to the conductive paste to be embedded and injected in thevia holes 414 and 416, besides silver paste, conductive paste and thelike including copper paste and conductive filler having copper powdercoated with silver may be used.

With respect to the relay board 410, since the conductive layer 412forming the wiring pattern, except for the interlayer conductiveportions 415 and 417, is coated with the insulating resin layer 413, andtherefore it is possible to omit the process for placing the cover layerfor protecting the conductor layer 412 forming the wiring pattern.

FIG. 30 shows a wiring board for partial multi-layer 430. The wiringboard for partial multi-layer 430 is formed by the following processes:A general-use single-sided copper coat polyimide base material that isthe same as the starting material of the relay board 410 is used as astarting material, a conductor layer 432 forming a wiring pattern isformed through etching, a via hole 433 is formed through a laser processor the like, and an interlayer conductive portion 434 is formed byembedding and injecting silver paste 437 in the via hole 433.

As shown in FIG. 30, prior to the lamination process onto the relayboard 410, the wiring board for partial multi-layer 430 is subjected toan outer-shape forming process (press punching process) and allowed tohave a predetermined shape corresponding to the plane shape of thepartial multi-layer portions 420A and 420B.

FIG. 31 show lamination processes of the wiring board for partialmulti-layer 430 manufactured through the above-mentioned processes. Asshown in FIG. 31A, predetermined numbers of wiring board for partialmulti-layers 430 having outer shapes that have been formed intopredetermined shapes are respectively positioned at specific areas onthe upper surface 413A of the insulating resin layer 413 and the rearsurface 410B of the insulating base material 411 of the relay board 410by using alignment marks, reference holes, circuit patterns or the like(not shown), and then superposed, and upper-surface and rear-surfaceouter-most-layer-use copper foils 437 are respectively placed on thesurfaces 430A of the insulating base materials 431 on the upper side(surface side) and the lower side (rear-surface side). Here, on therespective upper side and lower side of the relay board 410, the wiringboard for partial multi-layers 430 are laminated with the conductivelayer 432 side forming a wiring pattern facing the relay board 410 side.

Further, as shown in FIG. 31B, above members are heated andcontact-bonded under a high temperature and a high pressure by using avacuum cure pressing machine or a cure pressing machine so that a batchmulti-layer-forming process is carried out.

Lastly, as shown in FIG. 31C, the surface and rear-surfaceoutermost-layer-use copper foils 437 are respectively etched so that aconductor layer 435 forming a wiring pattern and component-packaging-useconductor land portions 436 are formed. Thus, a multi-layer wiring boardhaving partial multi-layer portions 420A and 420B is completed.

The conductor layer 435 forming the wiring pattern on the outermostlayer and the component-packaging-use conductor land portions 436 mayalso be formed by using a circuit-forming transfer tape 460 as shown inFIG. 32. The circuit-forming transfer tape 460 is formed on one surfaceof a carrier film 461 in a manner so as to allow the conductor layer 435forming the wiring pattern and the component-packaging-use conductorland portions 436 to be separated therefrom through etching or the like.

As shown in FIG. 33A, in place of the copper foil 437, thecircuit-forming transfer tape 460 is placed and positioned on thesurfaces 430A of the respective insulating base materials 431 on theupper side (surface side) and lower side (rear-surface side), with theconductor layer 435 forming the wiring pattern and thecomponent-packaging-use conductor land portions 436 being located on thesurface 430A side of the insulating base material 431. Moreover, afterthe curing process as shown in FIG. 33B, the carrier film 461 is removedas shown in FIG. 33C.

Thus, a multi-layer wiring board having the same properties as those ofthe aforementioned embodiments is provided. In this embodiment, theconductor layer 435 forming the wiring pattern on the outermost layerand the component-packaging-use conductor land portions 436 are pushedinto the insulating base material 431 of the wiring board for partialmulti-layer 430 through curing as shown in FIG. 33C. Therefore, it ispossible to obtain smooth surface layers of the partial multi-layerportions 420A and 420B.

FIGS. 34 and 35 show the other multi-layer forming processes inaccordance with the present embodiment. In this embodiment, as shown inFIG. 34, with respect to the surface and rear-surface outermost-layermembers, a conductor layer forming a wiring pattern of the outermostlayer, placed on one surface of the insulating base material 471, and anoutermost-layer-use wiring board for partial multi-layer 470 formed byetching the component-packaging-use conductor land portions 472 areused. The outermost-layer-use wiring board for partial multi-layer 470has an outer shape that has been formed into a predetermined shape inthe same manner as the multi-layer-use substrate 430, however, this hasno interlayer conductor portions.

As shown in FIG. 35A, in place of the copper foil 437, theouter-layer-use wiring board for partial multi-layer 470 is placed andpositioned on the surfaces 430A of the respective insulating basematerials 43 1 on the upper side (surface side) and lower side(rear-surface side), with the conductor layer forming the wiring patternand the component-packaging-use conductor land portions 472 beinglocated on the surface 430A side of the insulating base material 431,and subjected to a colamination process as shown in FIG. 35B.

Thereafter, as shown in FIG. 35C, component-packaging-use contact holes473, which penetrate the insulating base material 471 to be opened tocommunicate with the conductor land portion 472, are formed atpredetermined positions of the surface and rear-surface respectiveouter-layer-use wiring board for partial multi-layers 470. Thus, amulti-layer wiring board having partial multi-layer portions 420A and420B is completed.

The formation of the contact hole 473 is carried out by using an etchingprocess in which only the insulating base material 471 is fused byetchant, with predetermined portions other than the contact-hole openingportions being protected by chemical resistant resist. Moreover, thecontact holes 473 may be formed through a laser process using UV-YAGlaser, carbon dioxide laser or the like.

In the present embodiment, since the conductor layer forming a wiringpattern on the surfaces of the partial multi-layer portions 420A and420B is coated with the insulating base material 471, and therefore itis not necessary to separately prepare a cover layer for protecting theconductor layer forming the wiring pattern on the surfaces of thepartial multi-layer portions 420A and 420B. Moreover, as shown in FIG.33C, the component-packaging-use conductor land portions 472 are pushedinto the insulating base material 431 of the wiring board for partialmulti-layer 430 as shown in FIG. 33C. It is, therefore, possible toprovide smooth surface layers of the partial multi-layer portions 420Aand 420B.

Fourth Embodiment-Modified Embodiment

FIG. 36 shows another embodiment of a multi-layer wiring board inaccordance with the present invention. This multi-layer wiring board isprovided with a relay board 4110 such as a motherboard wiring board, andpartial multi-layer portions 4120A and 4120B formed by respectivelylaminating partial multi-layer substrates 4130 at specific portions onboth of the surface and rear-surface of the relay board 4110.

The relay board 4110 is comprised of a base material with single-sidedwiring circuit that is provided with a conductor layer (including aconductor land portion) 4112 performing as a wiring pattern, which isformed on one surface (upper surface 4110A) of an insulating basematerial 4111 that is made from polyimide or the like. An interlayerbonding layer 4141 is formed on the other surface of the insulating basematerial 4111 so that the insulating layer is allowed to have atwo-layer structure with the insulating base material 4111 and theinterlayer bonding layer 4141. With respect to the material for theinterlayer bonding layer 4141, thermosetting polyimide, thermoplasticpolyimide, thermoplastic polyimide to which a thermosetting property isimparted, liquid crystal polymer, epoxy resin and the like can be used.

On the conductor layer surface (upper surface 4110A) forming the wiringpattern if the insulating board 4111, an insulating resin layer 4113,which also performs as an interlayer bonding layer, is formed. Theinsulating resin layer 4113 may be formed the same material as thematerial of the interlayer bonding layer 4141.

With respect to the relay board 4110, interlayer conductive portions4115 and 4117 formed by via holes 4114 and 4116 are respectively formedin the insulating base material 4111, the interlayer bonding layer 4141and the insulating resin layer 4113. The interlayer conductive portions4115 and 4117 are constituted by the via holes 4114 and 4116 in whichconductive paste is embedded and injected.

On the surface of the interlayer bonding layer 4141 on the side oppositeto the insulating base material 4111, that is, the rear surface 4110Band the surface (upper surface 4113A) of the insulating resin layer4113, wiring board for partial multi-layers 4130 having outer shapesthat have been preliminarily formed into predetermined shapes arelaminated in conductive-association with the conductor layer 4112forming the wiring pattern of the relay board 4110 through theinterlayer conductive portion 4115 or 4117.

In the same manner as the relay board 4110, the wiring board for partialmulti-layer 4130 is also comprised of a base material with single-sidedwiring circuit that is provided with a conductor layer (including aconductor land portion) 4132 forming a wiring pattern, which is formedon one surface of an insulating base material 4131. An adhesive layer4142 is formed on the other surface of the insulating base material4131. With respect to the wiring board for partial multi-layer 4130, aninterlayer conductor portion 4134 is formed in the insulating basematerial 4131 and the adhesive layer 4142 through a via hole 4133. Theinterlayer conductive portion 4134 is also constituted by the via hole4133 in which conductive paste is embedded and injected.

With respect to the wiring board for partial multi-layer 4130, on theupper surface 4113A side of the relay board 4110, that is, on thepartial multi-layer portion 4120A, a plurality of them are laminatedwith the conductor layer 4132 forming a wiring pattern facing down, andon the rear-surface 4110B side of the relay board 4110, that is, on thepartial Iti-1a er portion 4120B, a plurality of them are laminated withthe conductor layer 4132 forming a wiring pattern facing up, thus, theselayers are bonded by the adhesive layers 4141 and 4142 or the insulatingresin layer 4113, which are located between layers. In other words, thewiring board for partial multi-layers 4130 are laminated on the upperside and the lower side of the relay board 4110 with the conductor layer4132 side thereof forming a wiring pattern facing the relay board 4110side.

On the surface 4130A of the adhesive layer 4142 of the wiring board forpartial multi-layer 4130 that forms the outermost layer of each of thepartial multi-layer portions 4120A and 4120B, a conductor layer 4135forming a wiring pattern and a component-packaging-use conductor landportion 4136 are formed.

With the above-mentioned structure, even when a lamination materialhaving a conductor layer such as copper foil formed on only one surfaceof the insulating base material 4111 is used as a starting material, apartial multi-layer structure is prepared at desired portions on both ofthe surface and rear surface of the relay board 4110, thereby allowingdouble-sided packaging processes. Moreover, by using the wiring boardfor partial multi-layer 4130 having an outer shape that has beenpreliminarily formed into a predetermined shape. It becomes possible toeliminate the necessity of preparing excessive multi-layer portions, andconsequently to cut the number of processes and the material costs.

With reference to FIGS. 37 to 39, a manufacturing method for amulti-layer wiring board to be used for the above-mentioned modifiedembodiment of the present embodiment will be described below.

FIGS. 37A to 37E show manufacturing processes of a relay board 4110. Asshown in FIG. 37A, a general-use single-sided copper coat polyimide basematerial (single-sided conductor coat lamination plate) 4150 is used asa starting material. The single-sided copper coat polyimide basematerial 4150 is a single-sided copper coat lamination plate (CCL)having copper foil 4151 placed as a conductor layer on only one of thesurfaces of the insulating base material 4111 made of a polyimide film.

First, etching resist is laminated on the copper foil 4151 of thesingle-sided copper coat polyimide base material 4150, and this issubjected to exposure to form a wiring pattern thereon, and thendeveloped. Thereafter, the exposed copper is etched through a cupricchloride bath to form a conductor layer (conductive pattern) 4112.Subsequently, the etching resist is removed so that a substrate withsingle-sided circuit 4152, shown in FIG. 37B, is formed.

As shown in FIG. 37C, on the surface of the insulating base material4111 opposite to the conductor layer surface (upper surface 4110A)forming a wiring pattern, an interlayer bonding layer 4141 is formed,and on the conductor layer surface (upper surface 4110A) forming awiring pattern of the insulating base material 4111, an insulating resinlayer 4113 which also performs as an adhesive layer, is formed. Theinsulating resin layer 4113 may be formed by a thermoplastic polyimideor the like, thus, by using the film-shaped material, a layering processcan be carried out on the upper surface 4110A of the insulating basematerial 4111 by using a contact-layering process, a laminating processor a vacuum laminating process through heat pressing or vacuum heatpressing. Moreover, the insulating resin layer 4113 may also be formedthrough a coating process such as a curtain coating process and a spincoating process by using a precursor varnish of a resin material.

Subsequently, as shown in FIG. 37D, a UV YAG laser beam a carbon dioxidelaser beam or the like is applied to a desired position to be used forinterlayer connection from the interlayer bonding layer 4141 side toform a via hole 4114 that penetrates the interlayer bonding layer 4141and the insulating base material 4111 to contact the rear surface ofcopper foil (conductor layer 4112 forming a wiring pattern). Moreover, aUV-YAG laser beam, a carbon dioxide laser beam or the like is applied toa desired position to be used for interlayer connection from theinsulating resin layer 4113 side to form a via hole 4116 that penetratesthe insulating resin layer 4113 to contact the upper surface of copperfoil (conductor layer 4112 forming a wiring pattern).

Subsequently; as shown in FIG. 37E, pieces of thermosetting silver paste4118 and 4119 are embedded and injected into the via holes 4114 and 4116through a print method or the like to form interlayer conductiveportions 4115 and 4117. Thus, a relay board 4110 is formed.

In this modified embodiment also, with respect to the relay board 4110,since the conductive layer 4112 forming the wiring pattern, except forthe interlayer conductive portions 4115 and 4117, is coated with theinsulating resin layer 4113. It is possible to omit the process forplacing the cover layer for protecting the conductor layer 4112 formingthe wiring pattern.

FIG. 38 shows a wiring board for partial multi-layer 4130. The wiringboard for partial multi-layer 4130 is formed by the following processes:A general-use single-sided copper coat polyimide base material that isthe same as the starting material of the relay board 4110 is used as astarting material, a conductor layer 4132 forming a wiring pattern isformed through etching, a via hole 4133 is formed through a laserprocess or the like, and an interlayer conductive portion 4134 is formedby embedding and injecting silver paste 4137 in the via hole 4133.

As shown in FIG. 38, prior to the lamination process onto the relayboard 4110, the wiring board for partial multi-layer 4130 is subjectedto an outer-shape forming process (press punching process) and allowedto have a predetermined shape corresponding to the plane shape of thepartial multi-layer portions 4120A and 4120B.

FIG. 39 shows lamination processes of the wiring board for partialmulti-layer 4130 manufactured through the above-mentioned processes. Asshown in FIG. 39A, predetermined numbers of wiring board for partialmulti-layers 4130 having outer shapes that have been formed intopredetermined shapes are respectively positioned at specific areas onthe upper surface 4113A of the insulating resin layer 4113 and the rearsurface 4110B of the insulating base material 4111 of the relay board4110 by using alignment marks, reference holes, circuit patterns or thelike (not shown), and then superposed one another. Further,upper-surface and rear-surface outer-most-layer-use copper foils 4137are respectively placed on the surfaces 4130A of the adhesive layer 4142on the upper side (surface side) and the lower side (rear-surface side).Here, on the respective upper side and lower side of the relay board4110, the wiring board for partial multi-layers 4130 are laminated withthe conductive layer 4132 side forming a wiring pattern facing the relayboard 4110 side.

Further, as shown in FIG. 39B, this is heated and contact-bonded under ahigh temperature and a high pressure by using a vacuum cure pressingmachine or a cure pressing machine so that a batch multi-layer-formingprocess is carried out.

Lastly, the surface and rear-surface outermost-layer-use copper foils4137 are respectively etched so that a conductor layer 4135 forming awiring pattern and component-packaging-use conductor land portions 4136are formed. Thus, a multi-layer wiring board having partial multi-layerportions 4120A and 4120B is completed.

In this modified embodiment also, the conductor layer 4135 forming thewiring pattern on the outermost layer and the component-packaging-useconductor land portions 4136 may be formed by using a circuit-formingtransfer tape that is the same as the circuit-forming transfer tape 460shown in FIGS. 32 and 33. Moreover, by using an outer-layer-use wiringboard for partial multi-layer that is the same as the outer-layer-usewiring board for partial multi-layer 470 as shown in FIGS. 34 and 35, astructure in which component-packaging-use contact holes are formed inthe outer-layer-use wiring board for partial multi-layer may beprepared.

INDUSTRIAL APPLICABILITY

In accordance with the present invention, at least one base materialhaving a wiring circuit that has been preliminarily formed into apredetermined outer shape is bonded to a motherboard, and these areelectrically connected to each other through at least an inner via hole.The outer shape of the base material having a wiring circuit is madesmaller than the outer shape of the motherboard with the base material,having a wiring circuit having an island shape on the motherboard.Therefore, it becomes possible to provide a higher design freedom forwiring, and consequently to cut material costs and achieve a reductionin the substrate capacitance.

Moreover, in accordance with the present invention, at least one basematerial with single-sided wiring circuit that has been preliminarilyformed into a predetermined outer shape is bonded to a motherboard, andthese are electrically connected to each other at least one portionthrough an inner via hole. The outer shape of the base material withsingle-sided wiring circuit is made smaller than the outer shape of themotherboard with the base material, having a wiring circuit having anisland shape on the motherboard. Therefore, it becomes possible toprovide a higher design freedom for wiring, and consequently to cutmaterial costs and achieve a reduction in the substrate capacitance.

Moreover, the base material with single-sided wiring circuit laminatedon the motherboard is positioned so that an outer shape of a second basematerial bonded to the first base material is located inside the outershape of the first base material on the motherboard side, and is allowedto have a pyramid shape, and therefore, upon bending the motherboard,stress imposed between the motherboard and the substrate withsingle-sided wiring circuit as well as between the laminated substrateswith single-sided wiring circuit can be dispersed and alleviated.Therefore, it becomes possible to provide high anti-bending strength(peel strength), and consequently to achieve a good bending propertythat is a feature of the multi-layer flexible printed wiring board(FPC).

Moreover, in accordance with the present invention, at least one portionof the insulating base material of the main single-sided circuitsubstrate is partially removed, and the rear surface of a conductivepattern is exposed at the removed portion, and from the other side ofthe insulating base material of the main single-sided circuit substrate,an electronic part is assembled in a state in which it isconduction-connected to the rear-face exposed portion of the conductivepattern, and/or a single-sided circuit board for multi-layer wiringboard having an interlayer conductive portion and a conductive patternformed on one face of an insulating base material is laminated in astate in which it is conduction-connected to the rear-faceexposed-portion of the conductive pattern. Moreover, on the other faceof the insulating base material of the main single-sided circuitsubstrate also, an electronic part is assembled and/or a single-sidedcircuit board for multi-layer wiring board is laminated so that it ispossible to provide a circuit substrate that allows double-sidedpackaging processes.

Furthermore, in accordance with the present invention, an insulatingresin layer, which also serves as an adhesive layer, is formed on theconductor layer surface side of a relay board, and an interlayerconductive portion derived from a conductive substance injected into avia hole formed in an insulating base material and an interlayerconductive portion derived from a conductive substance injected into avia hole formed in the insulating resin layer are prepared; therefore,even when a lamination material having a conductive layer such as copperfoil only on one surface of the insulating base material is used as astarting material, it is possible to partially prepare a multi-layerstructure at a desired portion on both of the surface and rear surfaceof the relay board, and consequently to allow double-sided packagingprocesses.

1. A multi-layer wiring board comprising: a motherboard; and at leastone base material having a wiring circuit which is formed into apredetermined outer shape and is laminated with the motherboard, whereinthe motherboard and the base material having a wiring circuit areelectrically connected to each other through an inner via hole.
 2. Themulti-layer wiring board according to claim 1, wherein the outer shapeof the base material having a wiring circuit is smaller than the outershape of the motherboard, and wherein the base material having a wiringcircuit is arranged on the motherboard to form an island shape.
 3. Themulti-layer wiring board according to claim 1 or claim 2, wherein aplurality of the base materials having a wiring circuit which is formedinto a predetermined outer shape are laminated on the motherboard. 4.The multi-layer wiring board according to any one of claims 1 or 2,wherein the base material having a wiring circuit comprises a basematerial with single-sided wiring circuit having an insulating layer anda wiring circuit formed on one surface of the insulating layer.
 5. Themulti-layer wiring board according to any one of claims 1 or 2, whereinan insulating layer of the motherboard is made of a flexible resin. 6.The multi-layer wiring board according to any one of claims 1 or 2,wherein the insulating layer of the base material having a wiringcircuit is made of a flexible resin
 7. The multi-layer wiring boardaccording to any one of claims 1 or 2, wherein the insulating layer ofthe motherboard and the insulating layer of the base material having awiring circuit are made of the same material.
 8. The multi-layer wiringboard according to any one of claims 1 or 2, wherein a cover layer forcoating the motherboard and the base material having a wiring circuit isformed.
 9. The multi-layer wiring board according to any one of claims 1or 2, wherein a cover layer having an opening is formed on themotherboard, and the base material having a wiring circuit is positionedin the opening.
 10. The multi-layer wiring board according to claim 9,wherein the wiring circuit of the motherboard is exposed in a gap whichis defined by the opening of the cover layer and the base materialhaving a wiring circuit, and wherein the wiring circuit of themotherboard is coated with noble-metal.
 11. The multi-layer wiring boardaccording to claim 9, wherein a second cover layer is formed so thatcoats the surface of the wiring board of the motherboard being exposedin a gap which is defined by the opening of the cover layer and the basematerial having a wiring circuit.
 12. The multi-layer wiring boardaccording to any one of claims 1 or 2, wherein, among the base materialshaving a wiring circuit accordingly, the insulating layer of the basematerial having a wiring circuit that contacts the motherboard is alsoperform as the cover layer that covers the wiring circuit of themotherboard.
 13. The multi-layer wiring board according to any one ofclaims 1 or 2, wherein the inner via hole in the base material having awiring circuit is filled with conductive paste for electrically connectdifferent layers one another.
 14. The multi-layer wiring board accordingto claim 13, wherein a small hall communicating with the inner via holeis pierced in a conductor layer of the base material having a wiringcircuit.
 15. A method for manufacturing a multi-layer wiring board,comprising the step of: laminating a base material having a wiringcircuit which is formed into a predetermined outer shape with at leastone of a surface and a rear surface of a motherboard.
 16. A method formanufacturing a multi-layer wiring board, comprising the steps of:forming a wiring circuit on at least one of a surface and a rear surfaceof the motherboard; making a via hole; and laminating a base materialhaving a wiring circuit which is formed into a predetermined outershape.
 17. The method for manufacturing a multi-layer wiring boardaccording to claim 15 or claim 16, wherein an outer shape of the basematerial having a wiring circuit is smaller than the outer shape of themotherboard.
 18. The method for manufacturing a multi-layer wiring boardof any one of claims 15 or 16 further comprising the step of: forming acover layer having an opening for positioning the base material having awiring circuit prior to the operation of laminating the base materialhaving a wiring circuit with the motherboard.
 19. The method formanufacturing a multi-layer wiring board according to any one of claims15 or 16 further comprising the step of: forming a cover layer forcoating the motherboard and the base material having a wiring circuitafter the operation of laminating the base material having a wiringcircuit with the motherboard.
 20. A multi-layer wiring board comprising:a motherboard; and at least two base materials with single-sided wiringcircuit, which are laminated with the motherboard, wherein themotherboard wiring board and the base material with single-sided wiringcircuit are electrically connected to each other through an inner viahole, and the at least two laminated base materials are positioned sothat the contour of one base material being laminated with the otherbase material is positioned inside the contour of the other basematerial being laminated with the motherboard.
 21. The multi-layerwiring board according to claim 20, wherein the contour of the basematerial with single-sided wiring circuit is smaller than the contour ofthe motherboard circumference of the base material with single-sidedwiring circuit is positioned inside circumference of the motherboard andwherein the base material with single-sided wiring circuit being formedinto an island shape on the motherboard viewed from the laminatingdirection of the base materials.
 22. The multi-layer wiring boardaccording to claim 20 or claim 21, wherein the motherboard comprises aninsulating layer made of a flexible resin.
 23. The multi-layer wiringboard according to any one of claims 20 or 21, wherein the base materialwith single-sided wiring circuit comprises an insulating layer made of aflexible resin.
 24. The multi-layer wiring board according to any one ofclaims 20 or 21, wherein the insulating layer of the motherboard and theinsulating layer of the base material with single-sided wiring circuitare made of the same material.
 25. The multi-layer wiring boardaccording to any one of claims 20 or 21, wherein a cover layer forcoating the motherboard is formed.
 26. The multi-layer wiring boardaccording to any one of claims 20 or 21, wherein the inner via hole ofthe base material with single-sided wiring circuit is filled withconductive paste to electrically connect different layers one another.27. A method for manufacturing a multi-layer wiring board, comprisingthe step of: laminating a base material with single-sided wiring circuitwhich is formed into a predetermined outer shape to at least one of thesurface and rear surface of the motherboard.
 28. A method formanufacturing a multi-layer wiring board comprising the steps of:preparing a resin plate to be used for a base material with single-sidedwiring circuit; forming a circuit portion on one surface of the resinplate; making a via hole that penetrates the resin plate from the onesurface to the other surface to reach at least one portion of thecircuit portion formed on the one surface of resin plate; injectingconductive paste into the via hole; provisionally curing the conductivepaste; dividing the base material with single-sided wiring circuit beingformed by previous steps into a plurality of base materials withsingle-sided wiring circuits; positioning the base materials withsingle-sided wiring circuits on the motherboard to be placed thereon;and laminating the base materials with single-sided wiring circuits andthe motherboard through a colaminating process while heating the basematerials and the motherboard so that a main curing process on theconductive paste is performed.
 29. A multi-layer wiring boardcomprising: a main single-sided circuit board which is comprised of ainsulating base material including a conductive pattern on one face ofthe insulating base material, wherein at least one portion of theinsulating base material is partially removed so that the rear face ofthe conductive pattern is exposed at the removed portion, and wherein atleast one of an electric part and a single-sided circuit board formulti-layer wiring board having an interlayer conductive portion and aconductive pattern formed on one face of an insulating layer iselectrically connected with a portion of the conductive pattern beingexposed from the rear side of the insulating base material.
 30. Themulti-layer wiring board according to claim 29, wherein an electronicpart is electrically connected with the conductive pattern of the mainsingle-sided circuit from the one side of the main single-sided circuitboard and a single-sided circuit board for multi-layer wiring boardwhich is comprised of an interlayer conductive portion and an insulatingbase material including a conductive pattern formed on one face of theinsulating base material is laminated so that the conductive pattern ofthe single-sided circuit board for multi-layer wiring board iselectrically connect with the conductive pattern of the mainsingle-sided circuit board.
 31. The circuit substrate according to claim29 or 30, wherein the main single-sided circuit board comprises aflexible wiring board.
 32. The multi-layer wiring board according to anyone of claims 29 or 30, wherein the main single-sided circuit boardfurther comprises a motherboard, and the contour of the single-sidedcircuit board for multi-layer wiring board is smaller than the contourof the motherboard, and wherein the single-sided circuit board formulti-layer wiring board is arranged to form an island shape on themotherboard.
 33. A method for manufacturing a multi-layer wiring board,comprising the steps of: forming a conductive pattern on a conductorlayer being formed on one surface of an insulating base material of alaminated board including conductor layer formed on one surface which isprocessed as a starting material of a main single-sided circuit board;removing a portion of the insulating base material of the mainsingle-sided circuit board so that a rear surface of the conductivepattern is exposed from the removed portion of the insulating basematerial; electrically connecting the conductive pattern being exposedin the removed portion with at least one of a electrical part from therear side of the insulating base material of the main single-sidedcircuit board and a conductive pattern formed on an insulating layer ofa single-sided circuit board for multi-layer wiring board having aninterlayer connecting portion; and electrically connecting at least oneof the conductive pattern on the one side of the main single-sidedcircuit board with a electrical part from the one side of the insulatingbase material of the main single-sided circuit board and the conductivepattern being exposed in the removed portion with a conductive patternformed on an insulating layer of a single-sided circuit board formulti-layer board having an interlayer connecting portion.
 34. Themethod for manufacturing a multi-layer wiring board according to claim33, wherein removing process of the insulating base material of the mainsingle-sided circuit board comprises an etching process or a laserprocess.
 35. The method for manufacturing a multi-layer wiring boardaccording to claim 33 or claim 34, wherein electrically connectingprocesses is carried out through a colaminating process.
 36. Amulti-layer wiring board comprising: a relay board which is comprised ofan adhesive insulating base material and a base material withsingle-sided wiring circuit having a conductor layer on one surface ofthe insulating base material; and a wiring board for partial multi-layerbeing laminated on a desired area of the relay board, wherein the relayboard further comprises an insulating resin layer formed on theconductor layer surface side, an interlayer conductive portion beingcomprised of a via hole which is filled with injected conductivesubstance and formed in the adhesive insulating base material and aninterlayer conductive portion being comprised of a via hole which isfilled with injected conductive substance and formed in the insulatingresin layer, and wherein the wiring board for partial multi-layers arelaminated on respective desired areas on the opposite surface of theconductive layer of the adhesive insulating base material and thesurface of the insulating resin layer so that the wiring board forpartial multi-layers are electrically connected with the relay boardaccordingly.
 37. A multi-layer wiring board comprising: a relay boardwhich is comprised of an insulating base material having a conductorlayer, an insulating resin layer coating the conductor layer and aninterlayer bonding layer; and a wiring board for partial multi-layerbeing laminated on a specific area of the relay board, wherein the relayboard further comprises an interlayer conductive portion being comprisedof a via hole which is filled with injected conductive substance andformed in the interlayer bonding layer and the insulating base materialand wherein the wiring boards for partial multi-layer are laminated onrespective desired areas on the surface of the interlayer bonding layerand the surface of the insulating resin layer so that the wiring boardfor partial multi-layers are electrically connected with the relay boardaccordingly.
 38. The multi-layer wiring board according to claim 36 orclaim 37, wherein the insulating resin layer of the relay board alsoperforms as an interlayer bonding layer.
 39. The multi-layer wiringboard according to any one of claims 36 or 37, wherein the wiring boardfor partial multi-layer further comprises a base material withsingle-sided wiring circuit that includes an adhesive insulating basematerial and a conductor layer being formed on the adhesive insulatingbase material, and wherein the wiring board for partial multi-layer islaminated with the relay board and land portions formed on the surfacesof the adhesive insulating base material of the both outer surface sideof the wiring board for partial multi-layers portion being laminated onboth sides of the relay board are electrically connected with aelectrical art.
 40. The multi-layer wiring board according to an one ofclaims 36 or 37, wherein the wiring board for partial multi-layerfurther comprises a base material with single-sided wiring circuit thatincludes an insulating base material an interlayer bonding layer coatingthe insulating base material and a conductor layer being formed on theinterlayer bonding layer, and wherein the wiring board for partialmulti-layer is laminated with the relay board, and land portions formedon the surfaces of the interlayer bonding layers of the both outersurface side of the wiring board for partial multi-layers portion beinglaminated on both sides of the relay board are electrically connectedwith a electrical part.
 41. The multi-layer wiring board according toany one of claims 36 or 37, wherein the wiring board for partialmulti-layer is comprised of a base material with single-sided wiringcircuit that has a conductor layer on an adhesive insulating basematerial, wherein the wiring board for partial multi-layer is laminatedwith the relay board under condition that the conductor layer surface ofthe wiring board for partial multi-layer being faced to the relay board,and wherein contact holes for electrically connecting with an electricalpart are formed in an adhesive insulating base material so that thecontact portions are communicated with land portions being formed onconductor layers of the wiring board for partial multi-layers of bothsides of the outermost partial multi-layer portions of the relay board.42. The multi-layer wiring board according to any one of claims 36 or37, wherein the wiring board for partial multi-layer is comprised of abase material with single-sided wiring circuit that includes aninsulating base material an interlayer bonding layer coating theinsulating base material and a conductor layer formed on the insulatingbase material, wherein the wiring board for partial multi-layer islaminated with the relay board under condition that the conductor layersurface of the wiring board for partial multi-layer being faced to therelay board, and wherein contact holes for electrically connecting withan electrical art are formed in an insulating base material and aninterlayer bonding layer so that the contact portions are communicatedwith land portions being formed on conductor layers of the wiring boardfor partial multi-layers of both sides of the outermost partialmulti-layer portions of the relay board.
 43. A method for manufacturinga multi-layer wiring board comprising the steps of: forming a circuit ona conductor layer formed on only one surface of an adhesive insulatingbase material of a wiring circuit board base material being processed asa starting material for a relay board; forming an insulating resin layercoating the conductor layer of the adhesive insulating base material;making via holes in the adhesive insulating base material and theinsulating resin layer of the relay board so that interlayer conductiveportions being filled with a conductive substance injected into the viaholes are formed in the insulating resin layer and the adhesiveinsulating base material; and laminating a wiring board for partialmulti-layer being preliminarily formed into a predetermined outer shapeat least on one of a specific area on the surface of the adhesiveinsulating base material and a specific area on the surface of theinsulating resin layer so that the wiring board for partial multi-layeris electrically connected with the relay board.
 44. A method formanufacturing a multi-layer wiring board comprising the steps of:forming a circuit on a conductor layer formed on one surface of aninsulating base material of a wiring circuit board base material beingprocessed as a starting material for a relay board; forming aninterlayer bonding layer on the other surface of the insulating basematerial of the wiring circuit board base material; forming aninsulating resin layer coating the conductor layer of the insulatingbase material; making via holes in the insulating base material theinsulating resin layer, and the interlayer bonding layer so thatinterlayer conductive portions being filled with a conductive substanceinjected into the via holes are formed in the insulating resin layer,the insulating base material and the interlayer bonding layer; andlaminating a wiring board for partial multi-layer being preliminarilyformed into a predetermined outer shape at least on one of a specificarea on the surface of the insulating resin layer and a specific area onthe surface of the interlayer bonding layer so that the wiring board forpartial multi-layer is electrically connected with the relay board. 45.A forming-use member in which a plurality of the base materials withwiring circuits to be used for the multi-layer wiring board disclosed inclaim 1 are formed.